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35-647: The Southern Oklahoma Aulacogen extends roughly 500 miles long (805 km) by ~80–90 miles wide (129–145 km). The two remaining continental plate boundary arms of the triple junction from which the Southern Oklahoma aulacogen formed became spreading zones for the spreading of the Iapetus Ocean during the breakup of the supercontinent, Rodinia , estimated to have occurred in the Cryogenian Period , approximately 750 million years ago. These arms closed in

70-462: A failed continental rift. The mountains themselves are Permian landforms covered and preserved by river-borne sediments in the Permian and partially excavated only in recent geological times. Exposure of these fossil mountains is greatest towards the southeast; much of the western part of the Permian range remains buried under sandstones and mudstones . The geologic history of the region began with

105-542: A section of plutonic and volcanic rocks that once formed the bedrock of the aulacogen, and as a result this aulacogen is "one of the best preserved and best exposed" selections of the igneous results of ancient rift activity. Consequently, the Southern Oklahoma Aulacogen is the designated type in the United States. The mafic rocks of the Southern Oklahoma aulacogen can be separated into two primary groups,

140-520: A system of transform faults . The Southern Oklahoma Aulacogen formed sometime in the Late Proterozoic Eon , between 525 and 550 million years ago, during the rifting of the Laurentia supercontinent or North American Craton, the geological core of North America. Its formation and bimodal igneous activity occurred simultaneously, with two definite episodes of magma activity, mafic and felsic ,

175-458: Is a distinct change in texture in the layers of granite, with earlier deposited layers being very fine-grained in comparison to later, coarse-grained granite layers. Some thought has been put forward as to the corresponding mafic intrusion needed to produce these felsic rocks, either through partial melting of the adjacent crust or through fractional crystallization of the mafic magma itself. Gilbert (1982) suggests that an igneous body related to

210-569: Is a short drive from Lawton and Walters . Bison , elk and deer are protected on the 59,020-acre (23,880 ha) wildlife refuge. The refuge also manages a herd of longhorn cattle. A scenic highway [Highway 115] traversing the park permits leisurely views of these and other fauna. Backcountry camping is available in the Charon Gardens Wilderness area . The park is home to a small number of fishing lakes. There are several trails for hiking. The Treasure Lake Job Corps site [now closed]

245-614: Is located here. Additional points of interest include the refuge 's visitors center, Holy City of the Wichitas, Quanah Parker Lake & Dam, Lake Jed Johnson , and Lake Lawtonka . Great Plains State Park is located near the geographic center of the Wichita Mountains, north of the town of Mountain Park . Quartz Mountain Nature Park and Arts Center is a recreation area located north of

280-447: Is very similar to the mid-Proterozoic age anorthosite - mangerite - charnockite - granite (AMCG) complexes of North America, but for the lack of coarse massif anorthosites. This is significant in that AMCG complexes tend to form at huge depths in the Earth's crust and thus cool more slowly, allowing the massif anorthosites to form coarse-grained. The similar igneous assemblage suggests that

315-738: The Ouachita orogenic belt . The Southern Oklahoma Aulacogen is associated with a widespread anomalous area in which seismic waves travel more slowly. A common comparison is drawn from this aulacogen to the Dniepr-Donets Aulacogen in Baltica because both are significant intracratonic rifts. The Southern Oklahoma Aulacogen contains numerous igneous rocks . Among these rocks are a multitude of gabbros , including anorthosite , titanium -rich, iron -rich, phosphorus -rich, and biotite gabbros. Also included are rhyolites and granites . This assemblage

350-627: The Pennsylvanian Period (~323.2–298.9 Ma) and formed part of the Ouachita orogenic belt . The Southern Oklahoma Aulacogen is estimated to contain over 250,000 km of igneous rock. The aulacogen is inverted: rather than extending across the surface it penetrates into the North American craton , and is aligned with the northern edge of a deeply buried Proterozoic basin of uncertain origin which may have formed through igneous layering or deposition. The aulacogen terminates on contact with

385-648: The Southern Oklahoma Aulacogen , being the result of a failed continental rift. The mountains are a northwest-southeast trending series of rocky promontories, many capped by 500 million-year old granite. These were exposed and rounded by weathering during the Pennsylvanian and Permian Periods. The eastern end of the mountains offers 1,000 feet (305 m) of topographic relief in a region otherwise dominated by gently rolling grasslands. The mountains are home to numerous working ranches and quarry operations,

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420-442: The magmas that formed the igneous rocks of the Southern Oklahoma Aulacogen quickly cooled to at or near their crystallization point, much more quickly than the magmas of AMCG complexes, thus resulting in finer-grained anorthosites. More recently, different interpretations of seismic and outcrop data, as well as stratigraphy in the area have led some studies to postulate that this formation may not be an aulacogen after all, but

455-403: The state reformatory , recreational homes and campsites, and scenic parklands. Fort Sill , home of the U.S. Army Field Artillery School , occupies a large portion of the southeastern end of the mountains. The Wichita Mountains National Wildlife Refuge , a favorite for hikers and rock climbers in the region, is located adjacent to Cache , Medicine Park , Indiahoma , and historic Meers , and

490-532: The Anadarko Basin, forming the Wichita Mountains . This also resulted in the reactivation of Cambrian rift faults, often becoming reverse or listric thrust faults . Anticlines formed in the sedimentary rock layers of the basin, contributing to the formation of the deep hydrocarbon reservoir of the Anadarko Basin. The formation of these listric faults and anticlines indicates that the crustal shortening

525-482: The Late Diabase Dikes may be responsible, despite the geochemical differences between the "wet" dikes and "dry" felsic rocks. Gilbert also points out that the predicted existence of a felsic-precursor mafic magma precludes the assumption that the positive Bouguer gravity anomaly is due only to the mafic rocks currently observed in the aulacogen. Due to its unique structure and faulting, the area within and around

560-554: The Mount Sheridan Gabbro, is exposed in roadcuts at Meers and underlies the Mount Scott Granite on the north side of the wildlife refuge. Weathered gabbroic soils are thicker and support more vegetation than those generated on weathered granite , so the tree line on the north side of Mount Sheridan approximates the contact between the Mount Sheridan Gabbro and the Mount Scott Granite. Geologic relationships suggest that

595-532: The Pennsylvanian and Permian Periods. Extensive weathering produced the tors of the Charon Gardens region and the "river" of boulders that descends the west slope of Mount Scott. Likewise, weathering produced the bowling-ball sized boulders in the Permian Post Oak Conglomerate locally found in and around the mountains. In addition to outcrops of the conglomerate, the boulders are preserved in

630-791: The Raggedy Mountain Gabbros and the Late Diabase Dikes. The Raggedy Mountain Gabbros can be further separated into two subgroups due to petrographic analysis and field mapping. These subgroups are the Glen Mountains Layered Complex and the Roosevelt Gabbros . The felsic rocks of the Southern Oklahoma aulacogen are broken into two main units, the Carlton Rhyolite Group and the Wichita Granite Group. There

665-483: The Wichita Mountains (including areas outside the refuge) is Haley Peak, at 2,481 ft (756 m). Haley Peak is located on private property just outside the northwest corner of the refuge. When the area was part of Indian reservations and therefore off-limits to non-Native Americans, the Wichita Mountains were rumored to contain rich gold deposits. When the area was first opened up for settlement, many prospectors staked mining claims, and towns were laid out to serve

700-479: The Wikimedia System Administrators, please include the details below. Request from 172.68.168.226 via cp1108 cp1108, Varnish XID 746812878 Upstream caches: cp1108 int Error: 429, Too Many Requests at Fri, 29 Nov 2024 05:36:51 GMT Wichita Mountains The Wichita Mountains are located in the southwestern portion of the U.S. state of Oklahoma . It is the principal relief system in

735-416: The area may have been, at one point, in the temperature range of the "liquid window," the range of temperatures that are ideal for oil formation. The isotherms of this window range from 65 °C to 150 °C. This further suggests that the area may have served as an oil formation bed before a late Ordovician fluid migration pulse. Continental plate Too Many Requests If you report this error to

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770-495: The aulacogen developed very deep basins (such as the Anadarko Basin ), forming excellent petroleum sources. Igneous rock deposits often form the hanging walls of anticline reverse faults in this area, leading to an unusual number of petroleum wells drilled into them in order to access the petroleum-bearing rock layers below. A graph of the geothermal history of the Southern Oklahoma Aulacogen suggests that sections of rock in

805-574: The cessation of magmatism , the region subsided and was inundated by a shallow sea, resulting in the deposition of detrital sediments followed by carbonates . The change marks the local expression of the Sauk Unconformity . The light-colored rocks exposed in the Slick Hills are lower Paleozoic marine sediments, and are equivalent to those exposed in the Arbuckle Mountains , 100 km to

840-609: The city of Altus . At 2,464 ft (751 m) Mount Scott is the second highest mountain within the Wichita Mountains National Wildlife Refuge boundary. Mount Pinchot in the Special Use Area is 12 feet (4 m) taller. A paved road leads to the summit of Mount Scott, offering views of the granite promontories to the west, the wind farm on the Slick Hills to the north, the lakes to the south and east, Fort Sill , and Lawton . The highest peak in

875-553: The dark gray rocks found throughout the Raggedy Mountains, the central lowlands region of the wildlife refuge, and to the immediate north of the refuge. Uplift and erosion followed, as the layered complex is unconformably overlain by the extensive lava flows of the Carlton Rhyolite Group. The rhyolites are a brown-red to orange porphyritic rock with 5–10 mm orange-colored alkali feldspar crystals. Most of

910-609: The deposition of late Precambrian to early Cambrian sandstones collectively known as the Tillman metasedimentary group. These sediments were intruded by a coarse mafic layered complex as the region began to rift apart during breakup of the Neoproterozoic continent, Pannotia . The exposed portion of this unit, named the Glen Mountains Layered Complex, consists of gabbro , anorthosite and troctolite . Recent high-precision dating yields an age of 532.49 ± 0.15 Ma. These are

945-886: The east. During the Pennsylvanian Period (330–290 million years ago) the region was subjected to intense pressure during the continental collision or orogeny which produced the Ouachita Mountains to the east. This resulted in faulting and folding striking along a WNW direction and includes the Arbuckle and Wichita Mountains of southern Oklahoma and the Amarillo Uplift of the Texas Panhandle . Up to 20,000 feet (6,100 m) of local uplift occurred during this time. This uplift locally created rugged mountains reduced by erosion to their present state largely during

980-411: The former of which being chiefly composed of gabbro-heavy magma and the latter phase being primarily composed of rhyolitic magma. It is hypothesized that between the mafic and felsic stages of magmatic activity substantial uplift occurred, which correlates to the lack of coarse-grained massif anorthosites presented previously. The remaining two arms of its original triple-junction became spreading zones for

1015-434: The granites and gabbros intruded at depths no greater than half a kilometer in the crust. Minor uplift ensued, and magmatism concluded with the intrusive emplacement of subvolcanic features: rhyolite and diabase dikes . These are poorly exposed, with the exception of a large diabase dike in the Mount Scott Granite revealed during the recent widening of Oklahoma State Highway 49 , just west of Interstate 44 . Following

1050-594: The nascent Iapetus Ocean . The aulacogen penetrated the craton, causing normal faults to form in what became the Anadarko Basin . The aulacogen underwent crustal shortening and inversion sometime in the Mississippian Period to the Early Permian Period , roughly 330–280 million years ago. This coincides with the closing of the Iapetus spreading zones and the overthrusting of the Ouachita uplift over

1085-449: The peaks and highlands in the eastern Wichitas and the isolated peaks of the western Wichitas. Some are equigranular , but most are porphyritic . The Mount Scott Granite is the most extensively exposed Wichita Granite. It forms the topographic feature from which it takes its name, and it is distributed throughout the northern half of the wildlife refuge. Dark rounded alkali feldspars , typically one centimeter or less in diameter, dominate

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1120-458: The porphyritic texture of this rock. SiO 2 levels in this granite range from 72.8% to 75.8%. Relatively small and compositionally distinct plutons , known as the Roosevelt Gabbros , are found in the eastern and central Wichita Mountains. Like the layered complex, these are dark rocks. Unlike the layered complex, they contain appreciable amounts of biotite , a mineral that forms in magmas with elevated dissolved water. One of these bodies,

1155-486: The presumed bonanzas, but no economic deposits were found. The gold boom was prolonged by some unscrupulous assayers who found gold in every sample, but the miners eventually gave up, leaving behind ghost towns such as Wildman, Oklahoma. The Wichita Mountains are rocky promontories and rounded hills made of red and black igneous rocks, light-colored sedimentary rocks, and boulder conglomerates. The Wichita Mountains were formed in four distinct geologic episodes following

1190-525: The rounded hills on Fort Sill are made of this rhyolite, including Medicine Bluffs. Additional exposure of the rhyolite is found in Blue Creek Canyon, where Oklahoma Highway 58 cuts through the Slick Hills. Tabular intrusions of granite and plutons of hydrous gabbro exploited the boundary between the layered complex and the rhyolites. The granites, collectively named the Wichita Granite Group, vary slightly in composition and texture. The granites form

1225-535: Was significant, up to 10–15 km or more. The igneous rocks found in the aulacogen were also uplifted during the Ouachita uplift and subsequently reburied by both local and transported sediments. As there was no major deformation of the midsection of North America during the Mesozoic and Cenozoic eras, the aulacogen's structure and rift assembly were mostly preserved. Erosion in recent eras has eroded sediments overlying

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